You ultimately can't deactivate it as you need to authenticate all accounts - there are no workarounds. If your reasoning for deactivating was to change the account that no longer exists for a different one on that platform then, Bungie disabled the ability to unlink platform accounts (except Twitch) from Bungie profiles back on [url=https://help.bungie.net/hc/en-us/articles/35597981889300-Notice-Bungie-net-Account-Unlinking-Update-on-March-25-2025]March 25 2025[/url]. Bungie also closed the workaround that let players without cross-save active move away from accounts they no longer had access to with that change, so even if you could deactivate cross-save without authenticating it - you cannot get around it. Bungie will not unlink the account under any circumstances.